Effect of high pressure processing of pork (Longissimus dorsi) on changes of protein structure and water loss during frozen storage

Protein and water modification in pork Longissimus dorsi (LD) pressurized at 200–400 MPa (5 min, 4 °C) followed by storage at −20 °C for up to 84 days were analyzed by complementary methodologies. Changes in proteins depended to a larger extent on storage time than pressure levels. High pressure (HP) improved drip loss by 35% after 84 days of storage. However, the meat's ability to retain water upon mechanical force (expressible moisture) was unaffected by both HP treatment and storage. No free water was present in the meat (due to drip loss), only immobile water and a larger fraction of water entrapped in the myofibrillar network were present. The water mobility after thawing was not affected as such by HP treatment and frozen storage. HP treatment and frozen storage results in a highly dynamic protein-water system, whereby protein and water molecules compete for H-bonding sites, consequently affecting the water binding.